This invention relates to an electrical switch assembly, and more particularly to a switch assembly used to carry large enough electrical loads so that arcing between switch contacts as they open is a factor to be dealt with.
Conventionally, a switch assembly of this type includes pairs of main contacts, one contact of each pair being stationary and the other movable, and pairs of arcing contacts, one arcing contact of each pair being stationary and the other movable. Each main stationary contact ordinarily carries a stationary arcing contact, and each movable main contact ordinarily carries a cooperable movable arcing contact. The pair of arcing contacts is designed to open only after the pair of main contacts open, so that no arc is drawn between the main contacts when they open, but instead the arc is drawn between the arcing contacts. Hence, any deterioration caused by the arc is limited to the arcing contacts which thereby protect the main contacts. Normally, therefore, as many pairs of arcing contacts are furnished as there are main contact pairs, and ordinarily are quenching means are provided for each pair of arcing contacts to extinguish the arc as quickly as possible.
It is an object of the present invention to provide an electrical switch assembly of reduced size and expense by eliminating the need for a separate pair of arcing contacts and a separate quenching means for each pair of main contacts.
It is another object of the invention to provide an electrical switch assembly in which only a single interrupter switch serves as the arcing contacts for all the pairs of main contacts, regardless of how many main contact pairs are present.
It is a further object of the invention to provide such a switch assembly in which the interrupter switch is a self-contained unit and physically separate from the main contacts, so that the interrupter switch can be removed from the switch assembly, for repair or replacement, without disturbing the main contacts and hence without the need to remove the switch assembly from service.
It is an additional object of the invention to provide such an assembly including an intermediate movable contact, movable with the main movable contact of the switch assembly, which maintains each circuit closed after the main movable contact separates from each stationary contact and before the circuit is opened by the interrupter switch.